JP2013213286A - Method for producing multilayer paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide multilayer paper that is excellent in a product appearance in the case where flat sheets of the paper are stacked and is excellent in printing workability during printing even when recycled pulp is highly blended.SOLUTION: The multilayer paper includes pulp as a main raw material and has a multilayer structure having 3 or more layers in which at least one inner layer is formed between a front layer and a rear layer. In the case where all layers from the front layer through the rear layer are stacked and measured, the absolute value of a fiber orientation angle in a region within 20% with respect to the paper making width of a paper machine from both end parts of the machine is 15 degrees or more at any place in the region. The fiber orientation angle between the front layer and the rear layer has a variation in a machine width direction of ±10 degrees or less over the entire width with respect to a paper making direction. The difference in the angles between the front and rear layers is 10 degrees or less over the entire width of the machine.

Description

  The present invention relates to multilayer paper. In particular, the present invention relates to a multilayer paper that can contain recycled pulp and is suitable as a flat printing paper.

In general, paper is roughly classified into paper and paperboard. There are various uses of the former paper, and postcards called “public postcards” (or “postcards”) and “private postcards” are one of them. A postcard is usually a postcard paper made from raw pulp and cut into a predetermined size. In the case of a government-made postcard, a face stamp printed with a face value that has the same effect as a stamp is printed. Printing is performed by offset printing or UV printing.
In recent paper production, the use of waste paper has been promoted due to increased environmental awareness such as recycling and resource saving. Patent Document 1 discloses a recycled postcard containing waste paper pulp and made by multi-layered stitching. The paper is listed.

JP 2010-047894 A

As described above, the postage sheet may have a fee stamp printed on the front surface and a pattern or the like printed on the back surface. These printings are performed by offset printing or UV printing. If the flat product has a poor appearance due to the upper part of the laminated flat product rising or the corners warping, the paper is fed by the paper feed unit. Since there is concern about defects, it becomes a cause of complaints at the printing shop. Further, dampening water adheres at the time of printing, the paper becomes weak, and conveyance failure occurs during printing, or moisture absorption and dehumidification occur due to the adhering and drying of the dampening water. For this reason, in a flat product that has been stacked in the printing unit after printing, the end (ear part) is warped or twisted, and some corners are raised, causing a jam in the paper discharge unit. There was a problem. In particular, when viewed in the machine width direction, the portion corresponding to the vicinity of the end portion has a smaller amount of shrinkage in the drying process at the time of manufacture than the portion corresponding to the vicinity of the center portion, so that the paper is weak and the CD direction (machine width) Direction) tends to be large in water. Recently, in consideration of the environment, it has been demanded to add a high proportion of recycled pulp made from waste paper. However, recycled pulp is weak due to the nature of its production, and CD direction (machine width direction) The elongation in water tended to be large.
Therefore, the present invention provides a low blend of recycled pulp, especially before and after printing, especially in the vicinity of the end in the machine width direction, with less warping and twisting, and no jamming during printing or at the paper discharge section. An object of the present invention is to provide a multi-layer paper suitable for large format printing.

  In multilayer paper, the inventors have adjusted the fiber orientation angle of each layer to make the amount of change and the difference between the front and back of the machine in a certain range, so that the dimensional stability and paper stiffness are good. And found that they can achieve the task.

The present invention includes, but is not limited to, the following inventions.
1. A method for producing a multilayer paper having a multilayer structure of three or more layers using pulp as a main raw material, wherein the following steps (1) to (3) are performed simultaneously or in any order, and then the step (4) How to do.
(1) In the surface layer, the side bleed valve opening and the J / W ratio are set such that the fiber orientation angle in the machine width direction is ± 10 degrees or less over the entire machine width.
(2) In the back layer, the fiber orientation angle in the machine width direction is ± 10 degrees or less over the entire machine width, and the difference in fiber orientation angle between the front and back layers is 10 degrees or less over the entire machine width. Set the W ratio.
(3) The J / W ratio condition of the inner layer other than the front and back layers is the same as that of the front layer, and the side bleed valve opening degree and / or the edge flow valve opening degree in the head box of the inner layer other than the front and back layers is adjusted, from the front layer to the back side. All the layers over the layers are overlapped, and the absolute value of the fiber orientation angle value in an area within 20% of the machine width of the machine from both ends of the machine is 15 degrees or more at any position in the area. The inner layer side bleed valve opening and / or edge flow valve opening is set.
(4) After adjusting the fiber orientation angle of each layer, the layers are combined.
2. A paper having a multilayer structure of three or more layers made of pulp as a main material and containing recycled pulp in at least one inner layer formed between the surface layer and the back layer, all layers from the surface layer to the back layer And the absolute value of the fiber orientation angle value in an area within 20% of the machine width of the machine from both ends of the machine when measured and measured is 15 degrees or more at any position in the area. The fiber orientation angle between the surface layer and the back layer is ± 10 degrees or less over the entire width in the machine width direction, and the difference between the fiber orientation angle of the entire surface layer and the fiber orientation angle of the entire back layer is 10 degrees or less over the entire machine width. Multi-layer paper.
3. 3. The multilayer paper according to 2, wherein the fiber orientation angle of the surface layer and the fiber orientation angle of the back layer in the machine width direction are both ± 10 degrees or less over the entire width.
4). The multilayer paper according to 2 or 3, wherein the difference between the fiber orientation angle of the surface layer and the fiber orientation angle of the entire back layer at an arbitrary point of the multilayer paper is 10 degrees or less over the entire width of the machine.
5. Elongation in water in the CD direction is 4% or less, and, multilayer paper according to any one CD direction Clark stiffness of 230 cm ^3/100 or more 2-4.

  According to the present invention, even when a high proportion of recycled pulp is used, the product is not warped or twisted before and after printing, and there is no occurrence of jam from the paper feed unit to the paper discharge unit. Can be provided.

1. Multilayer paper manufacturing method (multilayer paper structure)
The multi-layer paper of the present invention has a multi-layer structure of three or more layers made of pulp as a main material, and is made by a paper machine equipped with a plurality of head boxes, or a multi-layer paper made by a paper machine equipped with only a single head box. Manufactured by. For example, in the case of 3 layers, “surface layer”, “middle layer”, “back layer”, in the case of 4 layers, “surface layer” “front layer” “back layer” “back layer”, in case of 5 layers “surface layer” “surface layer” ”,“ Middle layer ”,“ back layer ”, and“ back layer ”. The number of stacked layers is not limited to these. The inner layer formed between the surface layer and the back layer in the present invention means “front layer”, “middle layer”, “back layer” and the like.

(Paper making method)
The multi-layer paper of the present invention is prepared by preparing a stock for each layer, and a known multi-layer paper machine such as a long net type paper machine, a twin wire paper machine, a Yankee paper machine, a circular net paper machine, and a short net combination machine. Possible paper machines can be selected as appropriate. In the present invention, a long net type wet paper machine is preferable.

Examples of the method for producing the multilayer paper of the present invention include the following methods. Note that the steps (1) to (3) need not be performed in this order, and the order can be arbitrarily changed.
(1) The opening degree of the side bleed valve in the head box for the surface layer is changed stepwise or steplessly, for example, 0%, 25%, 50%, 75%, 100% on both the operating side and the driving side, At each side bleed valve opening, the J / W ratio (= jet discharge speed ÷ wire speed × 100) is determined by the jet speed slower than the wire speed (J / W ratio <100%). The J / W ratio is successively increased at intervals of about 1% from 105% pressing to 95% pulling, centering on J / W ratio = 100%, until the state of fast pressing (J / W ratio> 100%). Only the surface layer is made by changing, and the side bleed valve opening degree and J / W ratio at which the fiber orientation angle in the machine width direction becomes ± 10 degrees or less with respect to the paper making direction over the entire machine width are grasped and set.

  With a multi-layer paper machine in a single headbox, it is difficult to make individual paper for each layer. Therefore, the J / W ratio for each layer is changed in sequence, and samples are collected in a state where the layers are combined, and then the J / W is collected. The fiber orientation angle is evaluated after peeling the layer with a tape until each layer with a changed ratio becomes a single body, and the relationship with the J / W ratio is grasped in advance. The side bleed valve is a valve provided on both sides of the head box. Since the raw material inside the head box escapes to both sides of the machine as the opening of the valve is opened, it is discharged onto the wire as an effect. The flow of the raw material jet from the head box is discharged with a large inclination in the outward direction, particularly at both sides of the machine. Accordingly, as the valve opening degree of the side bleed valve is increased, the angle of the fiber orientation near the both sides of the machine increases.

(2) Next, also in the head box for the back layer, similarly to the head box for the surface layer, the side bleed valve opening degree and the J / W ratio are sequentially changed so that the fiber orientation angle in the machine width direction extends over the entire machine width. It is set so that ± 10 degrees or less with respect to the paper making direction and the angle difference with the surface layer is 10 degrees or less over the entire width of the machine.
(3) Next, change the fiber orientation angle in the machine width direction by adjusting the side bleed valve opening and / or the edge flow valve opening by setting the J / W ratio conditions of the inner layers other than the front and back layers to the same conditions as the front layer. When measuring the absolute value of the fiber orientation angle in the region within 20% of the machine width of the machine from both ends of the machine by superimposing all the layers from the surface layer to the back layer, greater than 15 degrees In addition, the inner side side bleed valve opening degree and / or the edge flow valve opening degree which is 15 degrees or more at any position in the region is grasped and set.
(4) After adjusting the fiber orientation angle of each layer, the layers are combined.
Thus, in the present invention, the head layer of the surface layer is set to the side bleed valve opening and the J / W ratio at which the fiber orientation angle in the machine width direction is ± 10 degrees or less over the entire machine width with respect to the paper making direction, The head box for the back layer is a side bleed valve in which the fiber orientation angle in the machine width direction is ± 10 degrees or less over the entire machine width with respect to the paper making direction, and the difference in fiber orientation angle with the surface layer is 10 degrees or less over the entire machine width. Set the opening and J / W ratio. For the inner layers other than the front and back layers, all the layers from the front layer to the back layer are overlapped, and the fibers in the region within 20% of the machine width of the machine from both ends of the machine When the absolute value of the orientation angle value is measured, the side bleed valve opening degree and / or the edge flow valve opening degree that is 15 degrees or more at any position in the region is grasped and set.
Here, the fiber orientation angle in the machine width direction and the fiber orientation angle over the entire machine width indicate fiber orientation angles at arbitrary points in the machine width direction of the multilayer paper. Depending on the measurement position of the multi-layer paper in the machine width direction, it is normal that the measured value of the fiber orientation angle varies, but the fiber orientation angle in the machine width direction and the fiber orientation angle over the entire machine width in the present invention are in a specific range. This means that the range of the measured value of the fiber orientation angle, which varies, is within a specific range.
Further, in the present invention, the region within 20% of the machine width of the machine from both ends of the machine means 20% of the total width from the both ends of the multilayer paper produced by the machine toward the center in the width direction of the multilayer paper. It is an inner area until one by one.
Instead of the 20% or less area, it may be an area within 15% of the machine width from both ends of the machine, or a 20% area.
Then, all the layers from the surface layer to the back layer found as described above are overlapped, and the absolute value of the value in the machine width direction of the fiber orientation angle in the region within 20% of the machine width of the machine from both ends of the machine Is 15 degrees or more, and the fiber orientation angles of the front and back layers are ± 10 degrees or less over the machine width direction in the machine width direction and the difference between the fiber orientation angles of the front and back layers. Each layer is made according to the J / W ratio, the edge flow valve opening degree, and the side bleed valve opening degree that becomes 10 degrees or less over the entire width of the machine.

  Furthermore, in the multilayer paper of the present invention, it is preferable that the fiber orientation angle of the entire surface layer and the fiber orientation angle of the entire back layer are both ± 10 degrees or less. By setting such a fiber orientation angle, the curl height of the multilayer paper can be reduced, and coupled with the effect of improving the stiffness in the CD direction due to the larger fiber orientation angle of the inner layer, the multilayer paper as a whole is sufficient. It can have a good balance between rigidity and anti-curl properties.

  In addition to such properties, by making the difference between the fiber orientation angle of the surface layer and the fiber orientation angle of the entire back layer at an arbitrary point of the multilayer paper 10 degrees or less, at any point of the multilayer paper, by humidification or the like Generation of a twisting force can be prevented as much as possible, and as a result, generation of twisting curl of the entire multilayer paper can be suppressed.

(Fiber orientation angle and CD elongation in water)
The fiber orientation angle is a scale indicating the direction in which the fibers are arranged most. The larger the numerical value, the greater the inclination from the paper making direction. When the surface of the multilayer paper is facing upward and the papermaking direction is 12 o'clock, the clockwise direction is represented by + (plus), and the counterclockwise direction is represented by-(minus). Since fiber swelling and shrinkage during moisture absorption and dehumidification are performed in the minor axis direction of the fiber, if the fiber orientation angle is large, the elongation in water in the CD direction representing the degree of dimensional change in the CD direction is small. If the fiber orientation angle is small, the elongation in water in the CD direction increases, and both act directly. Therefore, if the fiber orientation angle difference between the front layer and the back layer in the multilayer paper is larger than 10 degrees, a difference in dimensional change when both layers absorb water causes warping, twisting, curling, wave out Cause.
In general, the elongation in water in the CD direction of multilayer paper produced at positions corresponding to both ends of the machine is larger than that produced near the center of the machine, and the dimensional stability is inferior. By superposing all the layers and increasing the absolute value of the fiber orientation angle in the machine width direction to 15 degrees or more, the underwater elongation in the CD direction at positions corresponding to both ends of the machine can be made 4% or less. I can do it.

In the present invention, it is important that the fiber orientation angles of the surface layer and the back layer in the machine width direction are ± 10 degrees or less over the entire machine width. When the fiber orientation angle of the surface layer and the back layer is ± 10 degrees or less and along the paper making direction, the curl of the flat product becomes a beautiful curl with the curl axis along the MD, and conversely, the surface layer and the back layer When the fiber orientation angle is out of the above range, warping and twisting of a flat product is likely to occur, and the product appearance tends to deteriorate. The fiber orientation angle can be evaluated by a microwave molecular orientation measuring device (manufactured by Oji Scientific Instruments) using a microwave as a measurement principle.
In the multilayer paper of the present invention, the elongation in water in the CD direction is desirably 4% or less. The elongation in water in the CD direction is determined by the JAPAN.TAPPI paper pulp test method no. 27: 2000, and paperboard--elongation in water test method A can be evaluated by method A.
(Fiber orientation angle and Clark stiffness)
Since the fiber orientation angle is the direction in which the fibers are arranged most, the Clark stiffness in the direction of the fiber orientation angle is high. In the vicinity of the end of the machine, the Clark stiffness in the CD direction is lower than that in the center of the machine due to the shrinkage during drying, but by increasing the fiber orientation angle to 15 degrees or more, the CD direction in the positions corresponding to both ends of the machine Clark stiffness it is possible to 230cm ^3/100 or more. Clark stiffness can be evaluated by the paper stiffness test method A using a JIS P-8143 Clark stiffness tester.

2. Multilayer paper Hereinafter, the multilayer paper of the present invention will be described in detail, but the present invention is not limited thereto.
(Pulp raw material)
The multilayer paper of the present invention has at least one inner layer. For example, in the case of 3 layers, in the “middle layer”, in the case of 4 layers, in the “front lower layer” and / or “back lower layer”, in the case of 5 layers Any one or more of the “front lower layer”, “middle layer”, and “back lower layer” may contain recycled pulp made from waste paper as a pulp.
In particular, in the present invention, recycled pulp does not have to be contained as a pulp raw material, but the recycled pulp can also have an arbitrary content ratio. When containing recycled pulp, it is preferable to use recycled pulp with a whiteness of 60% or more, which can solve problems caused by high blending of recycled pulp such as dirt and dust, and has excellent whiteness Can be obtained. The whiteness is measured according to JIS P 8148.
Moreover, when mix | blending recycled pulp with several inner layers by four or more layers, the recycled pulp mix | blended with each inner layer and / or a mixture ratio may be the same or different. When the whiteness of the regenerated pulp used for each layer is different, for example, when there are 5 or more layers, the whiteness of the regenerated pulp used for the front lower layer and the back lower layer is higher than the whiteness of the regenerated pulp used for the middle layer It is preferable. As a result, when the postcard paper is divided into layers, it is preferable that the whiteness of the front and back lower layer papers is higher than the whiteness of the middle layer paper.

In the case of using recycled pulp in the above, the inner layer is one of those generally used as a papermaking raw material such as mechanical pulp (MP), hardwood kraft pulp (LKP), conifer kraft pulp (NKP), or the like. Two or more types and recycled pulp can be mixed and used. Examples of the mechanical pulp include groundwood pulp (GP), refiner groundwood pulp (RGP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), chemiground pulp (CGP), semi-chemical pulp (SCP), and the like. .
From the viewpoint of the environment due to the reuse of resources, it is desirable that the amount of recycled pulp used is large. When using a mixture of recycled pulp and other pulp, the ratio of both in each layer can be arbitrarily set and is not particularly limited, but from the viewpoint of environmental aspects due to resource recycling, recycled pulp: other pulp = 50:50 to 100: 0 is preferable.
Used paper for recycled pulp includes high-quality paper, medium-quality paper, low-grade paper, newspaper, flyers, magazines, and other sorts of waste paper, unsorted waste paper mixed with these, copy paper, thermal paper, and carbonless paper. Office waste paper including the like can be suitably used.
On the other hand, recycled pulp may be added to the surface layer and the back layer, but chemical pulp such as softwood kraft pulp and hardwood kraft pulp may be used from the viewpoint of product whiteness, fluorescence intensity, dust and dirt, etc. preferable.
According to the present invention, a postcard paper in which recycled pulp is highly blended can be obtained. The content of the recycled pulp is preferably as much as possible from the environmental viewpoint, and is preferably 20% by mass or more, more preferably 40% by mass or more, and further preferably 60% by mass or more based on the total pulp solid content.

(Basis weight)
The basis weight of the multilayer paper is desirably 180 to 200 g / m ² . The basis weight range of each layer in the sheeting can be adjusted within a range not impairing the effect of the present invention, but the basis weights of the surface layer and the back layer are each preferably 20 to 60 g / m ² , 25 More preferably, it is ˜50 g / m ² . If the basis weight of the surface layer and the back layer is too low, there is a concern that the fluorescence intensity derived from the recycled pulp will be high. On the other hand, if the basis weight of the surface layer and the back layer is too high, the surface layer is good in terms of fluorescence intensity and dirt. The amount of chemical pulp used in the back layer is large, which is undesirable from a cost and environmental standpoint.
The basis weight of the inner layer is about 60 to 160 / ^{m 2} is preferred. When the recycled pulp is used and the paper is produced by making four or more layers (two or more inner layers), the basis weight of each layer is more preferably 30 to 80 g / m ² . If the basis weight of the inner layer is too low, the proportion of recycled pulp cannot be increased. On the other hand, if the basis weight of the inner layer is too high, the basis weight of the surface layer and the back layer will be reduced, and the fluorescence intensity derived from the recycled pulp will increase. There may be a problem in the readability of the destination information barcode.
If recycled pulp is not used, recycled pulp containing a large amount of ash is not used. As a result, less ash is contained in the multilayer paper, and recycled pulp with a relatively low whiteness is not used. As a result, the whiteness of the multilayer paper may become too high and the opacity may become low.

(Filler)
The multilayer paper of the present invention may contain a filler. The type of filler is not particularly limited. For example, calcium carbonate such as heavy calcium carbonate and light calcium carbonate, calcium carbonate-silica composite, titanium oxide, clay, silica, talc, kaolin, calcined kaolin, deramikaolin, magnesium carbonate , Inorganic fillers such as barium carbonate, zinc oxide, silicon oxide, amorphous silica, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, titanium oxide, bentonite; urea-formalin resin, polystyrene resin, melamine resin , Organic fillers such as phenol resin and fine hollow particles can be used alone or in appropriate combination of two or more. In addition, recycled fillers made from papermaking sludge, deinking floss, etc. can also be used. In the case of acidic papermaking, a filler obtained by removing acid-soluble ones from the filler is used, and the filler is used alone or in combination of two or more.

  In the present invention, in particular, since the paper can be recycled and the opacity and whiteness of the paper can be improved at a relatively low cost, the pH of the paper surface is adjusted to 6.0 to 9.5 using calcium carbonate. It is preferable to make a paper. If the content of the filler is too small, the opacity is inferior, and if it is too large, paper dust is likely to be generated during offset printing or cutting. The filler content mentioned here includes both those derived from recycled pulp and those added during papermaking.

(Paper chemicals)
In the present invention, various papermaking chemicals can be added as necessary. Specifically, polyacrylamide polymer, polyvinyl alcohol polymer, cationic starch, various modified starches, internal paper strength enhancers such as urea / formalin resin, melamine / formalin resin; rosin sizing agent, AKD type Sizing agents, ASA sizing agents, petroleum sizing agents, internal sizing agents such as neutral rosin sizing agents, and the like. In addition, a retention agent, a drainage improver, a coagulant, a sulfate band, bentonite, silica, a dye, an antifoaming agent, an ultraviolet ray inhibitor, a fading inhibitor, a pitch control agent, a slime control agent, and the like can be used.

(surface treatment)
The multilayer paper of the present invention can be coated with a surface treatment agent on one side or both sides as required. There are no particular limitations on the type and composition of the surface treatment agent, but examples of water-soluble polymeric substances for the purpose of improving surface strength include raw starch, oxidized starch, esterified starch, cationized starch, enzyme-modified starch, and aldehyde. Starch such as modified starch, hydroxyethylated starch, hydroxypropylated starch; cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and methylcellulose; modified alcohols such as polyvinyl alcohol and carboxyl-modified polyvinyl alcohol; styrene-butadiene copolymer, polyvinyl acetate, A vinyl chloride-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyacrylic acid ester, polyacrylamide or the like is used alone or in combination.

In addition, when the multilayer paper of the present invention is used for printing paper such as postcard paper, it is preferable that the Steecht sizing degree is 250 to 600 seconds in order to improve the writing ability or the printing ability with a printer. In order to increase the water absorption resistance as described above, a surface sizing agent such as styrene acrylic acid, styrene maleic acid, or an olefin compound may be applied in addition to the water-soluble polymer substance. The coating amount of the surface treatment agent is not particularly limited, and is usually about 0.5 to 5 g / m ² per both sides. Further, when a surface treatment agent comprising a water-soluble polymer substance and a surface sizing agent is applied, the mixing ratio of the water-soluble polymer substance and the surface sizing agent may be within a public range.
Moreover, when apply | coating the surface treating agent mentioned above, the coating apparatus can use what is generally used, for example, 2 roll size press, a gate roll coater, a rod metering size press, a blade coater, a bar blade coater Air knife coaters, curtain coaters, spray coaters, etc. can be used on-machine or off-machine.
Furthermore, in the present invention, a calendar process can be applied to the paper surface. There are no particular limitations on the type and processing conditions of the calendar device, and public devices such as ordinary calenders made of metal rolls, soft nip calenders, and high-temperature soft nip calenders are appropriately selected, and according to the quality target values, What is necessary is just to set conditions within the controllable range.

(Inkjet printing suitability)
The multilayer paper of the present invention can be given printability with an ink jet printer. The method for imparting ink jet printability is not particularly limited, and various techniques known in the field of ink jet recording paper may be applied. For example, as a coating type technique, an ink receiving layer containing a pigment and a binder is provided on the back side of a postcard (the side opposite to the side on which destination information is written). Further, when the ink receiving layer is provided by a cast coating method, a high-gloss and higher-quality image can be obtained. Examples of the plain paper type technique include addition of an oil-absorbing filler and an internal sizing agent, and application of a cationic resin as a dye fixing agent.

(Use of multilayer paper of the present invention)
In addition to postcard paper, the multilayer paper of the present invention can be used for printing paper, information paper, newsprint, packaging paper, paperboard such as liner and white paperboard, and the like. What is necessary is just to set suitably various physical properties, such as basic weight, a manufacturing method, etc. according to each use.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not restrict | limited to an Example. In the examples and comparative examples, parts and% represent solid parts by mass and solids mass%. In the following examples, five layers were combined, and each layer was described in the order of “surface layer”, “front layer”, “middle layer”, “back layer”, and “back layer”.

[Example 1]
(Raw material conditions for each layer)
The surface and back layers are 100 parts of LBKP beaten to 400 ml of Canadian Standard Freeness (CSF), 2 parts of calcium carbonate as filler, 0.4 part of internal sizing agent, 0.1 part of retention agent, sulfate band Was added to prepare a slurry. For the lower and lower layers, 50 parts of CSF 400 ml of LBKP and 50 parts of recycled pulp with a whiteness of 70% are mixed, and 0.75 parts of internal sizing agent and 2.5 parts of sulfuric acid band are added to prepare a slurry. did. The middle layer was prepared by adding 0.75 parts of an internally added sizing agent and 2.5 parts of a sulfuric acid band to 100 parts of 70% white recycled pulp.
(J / W ratio condition of each layer, edge flow valve opening condition, side bleed valve opening condition)
The paper making test was performed by changing the opening of the side bleed valve and the J / W ratio of the front and back layers in advance, and the head box of the surface layer has a variation in fiber orientation angle in the machine width direction of the surface layer of ± 10 degrees over the entire machine width. The side bleed valve opening and the J / W ratio were set as follows. The head box for the back layer has a side bleed valve opening degree and J / W at which the fiber orientation angle variation in the machine width direction is ± 10 degrees or less over the entire machine width and the angle difference with the surface layer is 10 degrees or less over the entire machine width. Set to ratio. The inner layers other than the front and back layers (front and lower layers, middle layer and back and lower layers) are machine widths of average fiber orientation angles when 5 layers of both the edge flow valve opening and the side bleed valve opening are stacked from the front layer to the back layer. The change in the direction was set to be 15 degrees or more in an area within 20% of the machine width of the machine from both ends of the machine.
(Making)
The above three types of paper stock slurry were paper-made with a long paper machine so that the surface layer = 28 g / m ² , the lower layer / middle layer / back layer = 44 g / m ² each, and the back layer = 30 g / m ² , Paper was made in the state of paper and dried, and the base paper was made with a J / W ratio of 102% for the surface layer, the surface lower layer, the middle layer, and the back layer so that the basis weight was 190 g / m ² . This base paper was coated with 1.8 g / m ² of polyvinyl alcohol on both sides with a two-roll size press and subjected to calendar treatment so that the Beck smoothness was 30 seconds to obtain a postcard paper.

[Example 2]
A postcard paper was obtained in the same manner as in Example 1 except that the edge flow valve opening degree of the front lower layer, the middle layer, and the back lower layer was adjusted and made. The opening degree of the side bleed valve other than the front and back layers at that time was 60%.
[Example 3]
A postcard paper was obtained in the same manner as in Example 1 except that the surface layer, the front lower layer, the middle layer, and the back lower layer were made with a J / W ratio of 101%.
[Example 4]
A postcard paper was obtained in the same manner as in Example 1 except that the edge flow valve opening degree of the front lower layer, middle layer and back lower layer was made in the closing direction.

[Comparative Example 1]
A postcard paper was obtained in the same manner as in Example 1 except that each layer was made at a J / W ratio of 102%.
[Comparative Example 2]
Postcard paper was obtained in the same manner as in Example 1 except that each layer was made with a side bleed valve opening of 25%.
[Comparative Example 3]
A postcard paper was obtained in the same manner as in Example 1 except that each side was made with a side bleed valve opening degree of 75%.
[Comparative Example 4]
A postcard paper was obtained in the same manner as in Example 1 except that the opening of the side bleed valve of the front lower layer, middle layer and back lower layer was made at 50%.
[Comparative Example 5]
A postcard paper was obtained in the same manner as in Example 1 except that the edge flow valve opening degree of the lower layer, middle layer and back layer was made at 60%.
Evaluation of the postcard paper obtained in each example and comparative example was performed by the following method. The evaluation results are summarized in Table 1.

[Measurement and evaluation method]
(Fiber orientation angle)
It measured with the microwave molecular orientation degree measuring apparatus (Oji Scientific Instruments Co., Ltd. product) using a microwave. The fiber orientation angle in the machine width direction was measured after sampling 20 locations at equal intervals from the machine operation side end to the drive side end with a sample size of 100 mm × 100 mm. The value of the fiber orientation angle of all layers from the surface layer to the back layer is 10 points at each end in the region within 20% of the machine width of the machine from both ends of the machine. The value having the smallest absolute value among the 20 points was adopted. In addition, the dispersion of the fiber orientation angle between the front layer and the back layer was determined by measuring the fiber orientation angle after dividing it by a tape into a single layer and measuring the absolute angle relative to the papermaking direction among the 20 places in the machine width direction. A value with a large value was adopted.
(Elongation in CD direction)
Similarly to the fiber orientation angle evaluation method, 20 points were sampled at equal intervals from the machine operation side end to the drive side end. After that, JAPAN. TAPPI Paper Pulp Test Method No. 27: 2000 Paper and paperboard-Underwater elongation test method Measured by the method A, and the value with the largest underwater elongation in the CD direction among the 20 locations in the machine width direction was adopted.
(Clark stiffness in CD direction)
Similar to the evaluation method of fiber orientation angle and underwater elongation in the CD direction, 20 points were sampled at equal intervals from the machine operation side end to the drive side end. Then, it measured by the paper stiffness test method A method using a JIS P-8143 Clark stiffness tester, and adopted the value with the smallest Clark stiffness in the CD direction among the 20 locations in the machine width direction.
(Jam during printing)
Print a 1120 mm (width) x 760 mm (vertical) postcard paper flat product in the order of indigo, red, yellow, and black at a printing speed of 8500 copies / hour on a sheet-fed press KOMORI LITRON RON 44 If it could be stacked on the paper part, it was rated as “◯”, and if a jam such as paper jam occurred on the way, it was marked as “x”.
(Evaluation of product appearance)
After printing, 5,000 flat sheets of 1120 mm (width) x 760 mm (length) postcard paper are stacked, and the height of the four corners of the top surface of the stack, and the height of the middle of the product in the width and length directions. Eight places were measured, and a height difference of 10 mm or more was evaluated as x, and less than 10 mm was evaluated as ◯.

From Table 1, the fiber orientation angle variation in the machine width direction of the surface layer is ± 10 degrees or less over the entire width, the fiber orientation angle variation of the back layer is ± 10 degrees or less over the entire width, and the angle difference with the surface layer is over the entire machine width. Less than 10 degrees, fiber orientation when all the layers from the surface layer to the back layer are overlapped and measured in the region within 20% of the machine width of the machine from both ends of the machine (region of both ends 20%) It can be seen that the postcard papers of Examples 1 to 4 having an absolute angle value of 15 degrees or more are excellent in product appearance because both the underwater elongation in the CD direction and the Clark stiffness are good, and there is little jam during printing. On the other hand, it can be seen that the postcard paper of the comparative example having a layer whose fiber orientation angle is out of range is inferior in dimensional stability, jam occurs during printing, and the product appearance is inferior.
Specifically, according to Comparative Example 1, the maximum absolute value of the fiber orientation angle of the back layer is large, and the minimum absolute value of the fiber orientation angle of the region within 20% of the machine width of the machine from both ends of the machine is As a result of being less than 15 °, the underwater elongation in the CD direction was high, the Clark stiffness in the CD direction was weak, jamming occurred during printing, and the product peak shape was poor.
Comparative Example 2 is an example in which the minimum absolute value of the fiber orientation angle in the region within 20% of the machine width of the machine from both ends of the machine is less than 15 °, and as a result, the elongation in water in the CD direction is high. The Clark stiffness in the CD direction was weak, and jamming occurred during printing. In Comparative Example 3, the fiber orientation angle in the machine width direction and the difference in fiber orientation angle between the front and back layers do not satisfy the requirements of the present invention. The result was bad.
Comparative Example 4 is an example in which the minimum absolute value of the fiber orientation angle in the region within 20% from the machine width of the machine from both ends of the machine is outside the range of the present invention, and as a result, the elongation in water in the CD direction is as a result. In addition, the Clark stiffness was inferior, jamming occurred during printing, and the mountain shape of the product was poor.
Comparative Example 5 is an example in which the minimum absolute value of the fiber orientation angle in a region within 20% of the machined width of the machine from both ends of the machine is outside the scope of the present invention as compared with Comparative Example 4, and therefore, comparison is made. Results were even worse than in Example 4.

Claims (5)

A method for producing a multilayer paper having a multilayer structure of three or more layers made of pulp as a main material and having at least one inner layer formed between a surface layer and a back layer, comprising the following (1) to (3 The method of performing the process of (4) after performing the process of) simultaneously or in arbitrary orders.
(1) In the surface layer, the side bleed valve opening degree and the J / W ratio are set such that the fiber orientation angle in the machine width direction is ± 10 degrees or less over the entire machine width.
(2) In the back layer, the fiber orientation angle in the machine width direction is ± 10 degrees or less over the entire machine width, and the difference in fiber orientation angle between the front and back layers is 10 degrees or less over the entire machine width. Set the W ratio.
(3) The J / W ratio condition of the inner layer other than the front and back layers is the same as that of the front layer, and the side bleed valve opening degree and / or the edge flow valve opening degree in the head box of the inner layer other than the front and back layers is adjusted, from the front layer to the back side. All the layers over the layers are overlapped, and the absolute value of the fiber orientation angle value in an area within 20% of the machine width of the machine from both ends of the machine is 15 degrees or more at any position in the area. The inner layer side bleed valve opening and / or edge flow valve opening is set.
(4) After adjusting the fiber orientation angle of each layer, the layers are combined.   A paper having a multilayer structure of three or more layers made of pulp as a main material and containing recycled pulp in at least one inner layer formed between the surface layer and the back layer, all layers from the surface layer to the back layer And the absolute value of the fiber orientation angle value in an area within 20% of the machine width of the machine from both ends of the machine when measured and measured is 15 degrees or more at any position in the area. The fiber orientation angle between the surface layer and the back layer is ± 10 degrees or less over the entire width in the machine width direction, and the difference between the fiber orientation angle of the entire surface layer and the fiber orientation angle of the entire back layer is 10 degrees or less over the entire machine width. Multi-layer paper.   The multilayer paper according to claim 2, wherein the fiber orientation angle of the surface layer and the fiber orientation angle of the back layer in the machine width direction are both ± 10 degrees or less over the entire width.   The multilayer paper according to claim 2 or 3, wherein the difference between the fiber orientation angle of the surface layer and the fiber orientation angle of the entire back layer at an arbitrary point of the multilayer paper is 10 degrees or less over the entire width of the machine. CD direction of elongation in water is 4% or less, and, multilayer paper according to any one of CD direction Clark stiffness is 230 cm ^3/100 or more of claims 2-4.